| Re: Overplotting 50% lines [message #39775] |
Mon, 14 June 2004 05:06 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Mark Douglas writes:
> I have a plot consisting of a strictly decreasing set of data (a
> distribution - percent of y greater than x) and I would like to
> overplot a 50% line onto this, that is one that comes across from 0.5
> on the y-axis, stops when it intersects the graph, then goes down to
> the x-axis.
>
> No matter what I do I can't get it to work. I'm either missing
> something really obvious or this is impossible. Any help please?
Seems to me the only "trick" will be finding the point
of intersection. I'd probably use VALUE_LOCATE to get
close, the interpolate (a simple linear interpolation
will work if your data is reasonably spaced) between
that point and the next. A couple of PLOTS commands
would draw the lines.
You can find a similar, although not exact, approach
to the problem here:
http://www.dfanning.com/graphics_tips/fillarea.html
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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